Memory devices for storing electrical charge are of considerable importance in DRAM technology, stacked capacitors, in particular having become widely used in this case. A storage capacitance of about 30 fF (femtofarads) is necessary, for instance, for DRAMs in the region of 4 gigabits or more. Conventionally, a basic area of typically 100×100 nm2 (nanometers2) is available for such a capacitance. In order to be able to realize the required capacitance on such a basic area, electrodes with an aspect ratio of greater than 100 are required with the customary materials for dielectrics. It is disadvantageous that such structures with such high aspect ratios made of silicon are mechanically unstable.
The document “Fundamental scaling laws of DRAM dielectrics”, by Reisinger, H.; Stengl, R., published in Proceedings of the 2000 Third IEEE International Caracas Conference on Devices, Circuits and Systems (Cat. No. 00TH8474), ISBN 0-7803-5766-3 publishes fundamental scaling laws of DRAM dielectrics. It is known according to the prior art that a relative permittivity must not exceed the value of 500 to 1000. For this reason, limits are disadvantageously imposed on increasing a storage capacitance through an increase in the relative permittivity of the dielectric of the storage capacitor of a memory device. In particular, the voltage across the memory cell limits an increase in the relative permittivity.
In order to increase the storage capacitance, it has been proposed to provide electrodes having an aspect ratio of greater than 100. It is disadvantageous that structures with such high aspect ratios are mechanically unstable.
Furthermore, it has been proposed to provide trench capacitors as capacitors of the memory device. The document “B. El-Kareh et al., The Evolution of DRAM cell technology, May 1997, Solid State Techn., pp. 89–101”, which is incorporated by reference, describes conventional semiconductor memory cells and the evolution thereof, in part with the use of trench capacitors. It is disadvantageous that the devices and structures described in the document do not provide structures with a high aspect ratio. A capacitance for storing electrical charge is limited in this way.